This application is based upon and claims benefit of priority from the prior Japanese Patent Application No. 2000-189479, filed on Jun. 23, 2000; the contents of which are incorporated herein by reference.
1. Field of The Invention
The present invention relates generally to an image processing system and method, and an image display system.
2. Description of Related Art
As conventional image display devices, there are two types of impulse type display devices (e.g., CRTs, field emission type display devices (which will be hereinafter referred to FEDs)), which continue to emit light only for the afterglow time of a fluorescent substance after writing an image, and hold type display devices (e.g., liquid crystal displays (which will be hereinafter referred to as LCDs), electroluminescent displays (which will be hereinafter referred to as ELDs)), which continue to hold the display of the last frame until a new image is written. There are also plasma display panels (which will be hereinafter referred to as PDPs) and projectors using a film. The PDP is a system for carrying out a gradation display in time axis directions, which is called a pulse width modulation method, so that the PDP is considered as a kind of hold type. The projector using a film is considered as a hybrid type for carrying out irradiation and non-irradiation of an image for a frame period. As other systems of a hybrid type, a system using a LCD and a shutter has been proposed by Japan Association of Broadcasters (see Japanese Patent Laid-Open Publication No. 1997-325715), and a system using a LCD and a flashing back light has been proposed by International Business Machines Corporation (see Japanese Patent Laid-Open Publication No. 1999-109921).
The hold type display device has a problem in that the blurred phenomenon and the discontinuous display phenomenon are caused during the display of a moving picture. As shown in FIG. 16, the blurred phenomenon is caused by the fact that if observer""s eyes track the movement of a moving object, the eyes observe the picture while moving on the last frame picture, although the same picture of the last frame continues to be displayed in a frame before the picture of the next frame is displayed. That is, the tracking motion of eyes has continuity, so that fine sampling is carried out. As a result, blurring is observed by carrying out visual recognition so that a picture between the first frame and the second frame is buried. On the other hand, the discontinuous display phenomenon is particularly observed in the case of a fixation viewpoint, and is based on the fact that pictures of several frames are substantially simultaneously observed as shown in FIG. 17. These phenomena depend on the speed of the moving object. If the speed of the moving object increases, the correlation between the last frame picture and the next frame picture deteriorates, so that the phenomena are more conspicuously observed.
On the other hand, the impulse type display device has a problem in that the picture jumping phenomenon is caused during the display of a moving picture. Although this picture jumping phenomenon is observed similar to the above described discontinuous display phenomenon, it is described by a different expression since the cause of occurrence is different from that of the discontinuous display phenomenon. The picture jumping phenomenon is also particularly caused at a fixation viewpoint. In the impulse type display device, since display disappears between frames, in other words, a picture having no correlation right before a next frame is not displayed, so that blurring decreases. On the contrary, the picture jumping phenomenon is more conspicuously visually recognized even in usual observation circumstances. The picture jumping phenomenon depends on the speed of a moving object and a frame frequency (the reciprocal of a frame period). It is considered that the reason why the picture jumping phenomenon is caused is as follows. If the speed of the moving object increases with respect to the frame frequency, although a correct image is projected on retinas in time series, the image between the last frame and the next frame disappears as shown in FIG. 18, so that the interpolation processing is not sufficiently carried out in brains.
Thus, in conventional image display devices, there is a problem in that the picture quality deteriorates in accordance with the displayed contents. It seems that the deterioration of the picture quality is more conspicuous with the increase of images having clear contours, i.e., images including high spatial frequency spectra, such as images obtained by computer graphics or the like and images picked up by a high-speed shutter video camera.
According to one aspect of the present invention, an image processing method comprises: incorporating input frame pictures to be displayed on a display device, on the basis of an input picture signal and an input synchronizing signal which is synchronized with the input picture signal; recording the incorporated frame pictures in an input frame memory; and producing output frame pictures from input frame pictures, which have been recorded in the input frame memory, by producing an interpolated picture or inserting a black raster picture or thinning out the input frame pictures, between input frame pictures corresponding to a picture information of the input frame picture to be displayed, on the basis of the picture information and the input synchronizing signal and an output synchronizing signal.
The production of the output frame pictures may comprise: comparing the refresh rate of the input frame pictures with the refresh rate of the output frame pictures; outputting the input frame pictures as the output frame picture, or outputting the input frame pictures, between which the black raster picture is inserted, as the output frame pictures, when the refresh rate of the input frame pictures is equal to the refresh rate of the output frame pictures; producing an interpolated picture between the input frame pictures, or outputting the input frame pictures, between which the black raster picture is inserted, as the output frame pictures, when the refresh rate of the output frame pictures is higher than the refresh rate of the input frame pictures; and thinning out the input frame pictures, or producing an interpolated picture between the input frame pictures, or outputting the input frame pictures, between which the black raster picture is inserted, as the output frame pictures, when the refresh rate of the output frame pictures is lower than the refresh rate of the input frame pictures.
The picture information may include information which indicates whether the picture to be displayed is a moving picture or a still picture, and the method may further comprise discriminating whether the picture to be displayed is a moving picture or a still picture.
The discriminating may comprise: incorporating frame pictures of the picture to be displayed, at regular intervals on the basis of the input picture signal and the input synchronizing signal; and
obtaining the correlation between two input frame pictures which have been continuously incorporated, the method discriminating whether the picture to be displayed is a moving picture or a still picture on the basis of the correlation result.
The discriminating may comprise determining whether the moving picture is in a first state in which the motion of a moving object in the moving picture is rapid, or in a second state in which the moving speed of the moving object is slower than that in the first state, on the basis of the correlation, when it is determined that the picture to be displayed is a moving picture.
The correlation may be obtained on the basis of the difference between pixels corresponding to the continuously incorporated two input frame pictures.
The correlation may be obtained on the basis of the scalar quantity of a motion vector.
When it is discriminated that the picture to be displayed is a moving picture and when it is determined that the moving speed of the moving object in the moving picture is in the first state, the production of the output frame pictures may comprise: comparing the refresh rate of the input frame pictures with the refresh rate of the output frame pictures; outputting the input frame pictures as the output frame picture, when the refresh rate of the input frame pictures is equal to the refresh rate of the output frame pictures; producing an interpolated picture between the input frame pictures to output the interpolated picture, when the refresh rate of the output frame pictures is higher than the refresh rate of the input frame pictures; and thinning out the input frame pictures to produce and output the output frame pictures, when the refresh rate of the output frame pictures is lower than the refresh rate of the input frame pictures.
The display device may be an impulse type display device, and when it is discriminated that the picture to be displayed is a moving picture and when it is determined that the moving speed of the moving object in the moving picture is in the second state, the production of the output frame pictures may comprise: comparing the refresh rate of the input frame pictures with the refresh rate of the output frame pictures; outputting the input frame pictures as the output frame picture, when the refresh rate of the input frame pictures is equal to the refresh rate of the output frame pictures; stopping the output of signals between the input frame pictures, or inserting and outputting a black raster picture, when the refresh rate of the output frame pictures is higher than the refresh rate of the input frame pictures; and thinning out the input frame pictures to produce and output the output frame pictures, when the refresh rate of the output frame pictures is lower than the refresh rate of the input frame pictures.
The display device may be a hold type display device, and when it is discriminated that the picture to be displayed is a moving picture and when it is determined that the moving speed of the moving object in the moving picture is in the second state, the production of the output frame pictures may comprise: comparing the refresh rate of the input frame pictures with the refresh rate of the output frame pictures; outputting the input frame pictures as the output frame picture, when the refresh rate of the input frame pictures is equal to the refresh rate of the output frame pictures; stopping the outputs of the output picture signal and the output synchronizing signal between the input frame pictures, when the refresh rate of the output frame pictures is higher than the refresh rate of the input frame pictures; and thinning out the input frame pictures to produce and output the output frame pictures, when the refresh rate of the output frame pictures is lower than the refresh rate of the input frame pictures.
When it is discriminated that the picture to be displayed is a still picture, the production of the output frame pictures may comprise: comparing the refresh rate of the input frame pictures with the refresh rate of the output frame pictures; outputting the input frame pictures as the output frame picture, when the refresh rate of the input frame pictures is equal to the refresh rate of the output frame pictures; displaying the same picture between the output frame pictures, or stopping the output of signals between the input frame pictures, when the refresh rate of the output frame pictures is higher than the refresh rate of the input frame pictures; and thinning out the input frame pictures to produce and output the output frame pictures, when the refresh rate of the output frame pictures is lower than the refresh rate of the input frame pictures.
The interpolated picture or the black raster picture may be selected in accordance with the magnitudes of a spatial frequency and frequency spectra in one frame picture.
Alternatively, the interpolated picture or the black raster picture may be selected in accordance with the speed of a moving object in the picture to be displayed.
According to another aspect of the present invention, an image processing system comprises a picture signal converting part converting an input picture signal, which is a picture signal for a picture to be displayed on a display device for displaying a picture while changing the picture every frame picture, and an input synchronizing signal, which is synchronized with the input picture signal, into an output picture signal, which is a picture signal for a picture suitable for the display device, and an output synchronizing signal which is synchronized with the output picture signal, on the basis of picture information of the picture to be displayed on the display device, the picture signal converting part comprising: an input frame memory in which a frame picture is recorded; an input switching part transmitting a input frame picture to be displayed, to the input frame memory on the basis of the input picture signal and the input synchronizing signal; a black raster picture producing part in which a black raster picture has been produced or stored; a picture converting part producing output frame pictures from input frame pictures, which have been recorded in the input frame memory, by producing an interpolated picture or inserting a black raster picture or thinning out the input frame pictures, between input frame pictures corresponding to the picture information, on the basis of the picture information and the input synchronizing signal and the output synchronizing signal; an output frame memory recording therein the output frame pictures; and an output control switching part taking the output picture signal and the output synchronizing signal out of the output frame pictures, which have been recorded in the output frame memory, to transmit the signals to the display device.
The picture signal converting part may include priority processing means for spatial-frequency-dividing one frame picture and using an interpolated picture, not a black raster picture, as an output frame picture, with respect to a picture containing high frequency spectra.